. Prostate specific antigen (PSA) screening to prevent death and disability from prostate cancer has come into widespread use in the U.S. since 1989. The American Cancer Society recommends that all men over age 50 have this blood test done annually, and there is evidence that a majority of 50-79 year old men have had the test at least once. While screening has led to a major increase in the diagnosis of cancer and, consequently, i radical prostate surgeries, its efficacy in preventing death from this disease is unproven. Prostate cancer mortality has continued to increase. A population-based, case-control study of PSA screening is proposed as the most timely approach to evaluate this major screening modality. These studies have been used successfully to evaluate other screening modalities and are predicated on the notion that if screening prevents mortality, the decedents should be less likely to have been screened than comparable men in the population. Cases will be 55-79 year old, married, New Jersey men, dying of prostate cancer in 1998-2000. Married controls will be selected from random digit dialing (age 55-64) or from Federal Medicare files (age 65-79) and will be matched to cases on age and race. Case and control families will be interviewed to ascertain all sources of medical care since 1989 and secure permission to review these records for PSA screening. All inpatient and outpatient providers will be contacted to ascertain instances of PSA screening since 1989. Analysis will focus on whether or not cases were screened from 1989 to the time of diagnosis. An exactly comparable calendar time period will be studied in controls. The extent of protection (measured as an odds ratio for prostate cancer death of less than 1.0) associated with screening will be calculated before and after adjustment for potential confounders. This study is proposed to provide the first direct estimate of the effectiveness of PSA screening on prostate cancer mortality.